/Engine/Source/Editor/UnrealEd/Public/Subsystems/PanelExtensionSubsystem.h
Delegate that generates theSExtensionPanelcontent widget. TheFWeakObjectPtrparam is an opaque context specific to the panel that is being extended which can be used to customize or populate the extension widget.
typedef TBaseDelegate_OneParam< [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) >, [FWeakObjectPtr](API\Runtime\CoreUObject\UObject\FWeakObjectPtr) > FCreateExtensionWidget